(1) Field of the Invention
The invention relates to an apparatus for supporting pipe lines or the like on a supporting structure.
(2) Description of the Prior Art
U.S. Pat. No. 2,159,870 to E. A. Wert discloses a spring shackle for the suspended support of a pipe line. The device includes a cylindrical spring housing with an upper cover plate suspended from the supporting structure and a lower housing bottom. A cylindrical pressure spring is arranged within the housing. Above the pressure spring is a spring rest. A threaded spindle depends from the spring rest and a turnbuckle is provided. The pipe line is suspended via a pull rod screwed into the turnbuckle. By rotating the turnbuckle, the spring force is adjusted for operation.
The spring force adjustment in this structure is intended to be carried out in such a way that the pipe line is positioned with relation to the supporting structure at a precisely prespecified level, i.e., free of bending strain, and at equilibrium. This adjustment operation is often difficult, since it cannot be determined from the outside whether the pipe line arrangement is free of strain or whether strain may still exist in an apparently correctly suspended pipe line.
It has therefore become customary to pre-calculate the forces to be absorbed by the individual spring shackles in a pipe line system and to preset the spring force of the spring shackles accordingly in the factory. The presetting is achieved by compressing the spring so that it exerts a force corresponding to the load which the shackle will support and then maintaining that degree of compression by a blocking device. Since, as just indicated, the presetting corresponds to the load to be absorbed by the spring shackle when installed, nothing changes at the removal of the blocking device if the pipe line has been suspended at the correct level by means of the spring force lock, and the pipe line, freely suspended from the pressure spring, is in equilibrium.
Another reason for the provision of blocking devices is that, in the construction of pipe line systems that are supported by spring shackles, a temporary overloading often cannot be avoided. This will happen, for example, when completely installed steam lines are later treated with a pickling fluid and the total weight of the pipes during the pickling cycle amounts to a multiple of the weight of the pipe lines when they are in condition for operation with the steam cycle. Thus, blocking devices are also customary for the purpose of absorbing overloads of the pressure spring caused by such temporary load increases.
U.S. Pat. No. 2,936,142 to P. C. Sherburne discloses a blocking device wherein "T" sections are inserted into a longitudinal slot of the spring housing. The transverse portions of the "T" sections abut against the outside of the housing and the leg portions of the "T" sections, act against the spring rest in order to lock the latter in the longitudinal direction. In the case of the "hot" load blocking, i.e., in the blocking of the pipe line against a load corresponding to its normal steam-carrying state, the "T" sections are inserted between the upper side of the spring rest and the upper end of the longitudinal slot. In "cold" load blocking, i.e., in blocking against higher loads, the "T" sections are inserted between the lower side of the spring rest and the lower end of the longitudinal slot. Of course, both measures can also be taken simultaneously. The "T" sections are secured against sliding out of the slots by wires wound about the spring housing and the "T" sections.
U.S. Pat. No. 2,713,982 to W. A. Sherbrooke discloses another type of blocking device wherein radial screw bolts engage the spring housing from the outside to act against the spring rest and lock it at a specific level.
Both types of blocking devices present the common disadvantage that blocking is possible with a specific spring presetting only and, in the case of the "T" sections of U.S. Pat. No. 2,936,142, it is necessary to specifically cut each blocking device to size for each spring shackle. This requires substantial work and therefore substantial expense. Moreover, storing of the blocking elements for subsequent shutdown and overhaul of the pipe line system is impractical, and, in practice, it is likely either that the blocking devices will be lost or that they will become unsorted. It is also a particular disadvantage that the blocking elements, on account of deviations in calculated force values from actual conditions, usually no longer fit after the first mounting.
As to the device disclosed in U.S. Pat. No. 2,936,142, there is also the disadvantage that during the "cold" load blocking, the inner diameter of the spring housing and the outer diameter of the spring rest must be considerably larger than the outer diameter of the spring. Otherwise, there cannot be a safe support of the spring rest against large loads, since large deflections would cause expansion and consequent obstruction of the pressure spring. Therefore a larger form of structure must be accepted and the stabilization and guidance of the pressure spring is impaired.